|
Overview of research theme
in our group where we combine the
synthesis of 2D materials such as
graphene with fundamental studies of
colloidal phases and flow behaviour
to arrive at industrially-adaptable
manufacturing and fabrication
methods in developing efficient
graphene-based platforms for clean
energy, chemical separations and
micro-/nano-fluidics.
Graphene-based energy materials and
devices program:
Most of the research activity
centers around exfoliation of
graphite in liquid phase
predominantly as a highly oxidized
and water soluble precursor –
graphene oxide (GO). Graphite is a
naturally occurring mineral deposit
which serves as a cheap source for
these advanced materials, thus
highlighting a significant value
addition to this mineral resource.
Graphene-based materials because of
their monoatomic thickness possess
massive surface area, large
electrical conductivity, mechanical
flexibility and can be processed
easily in the fluid phase. The
energy program endeavours to develop
novel energy storage materials,
architectures and devices in the
space of super-capacitors and
batteries.
Miniaturization of energy storage
devices:
Microarchitecture plays a
significant role in enhancing the
power and energy density of
super-capacitor devices. If two
electrodes can be spaced very close
to each other with micron-scale
resolution and the dimensions of
each electrode could be
miniaturized, electrode kinetics
will be dramatically enhanced and
active electrode surface area could
be much better utilized. The upshot
of miniaturization is that the
reduced dimensions not only have
very large energy and power
densities, but also can be densely
packed in a given area.
Graphene-oxide (GO), which is
essentially an insulator, can be
processed into continuous films and
conductive pathways in the GO film
can be imprinted by different
irradiation techniques such by using
laser, UV radiation and ion-beams
enabling precise pattering
methodologies [1]. A significant
aspect of the program will focus on
the chemical reduction mechanisms,
microstructure and carbon structure
evolution, and how patterning
approaches could be developed based
on these fundamentals. The second
aspect of the program will focus on
measurement of electrochemical
properties in wide ranging
electrolytes to unearth how carbon
structure, electrolytes and
microarchitecture affect energy and
power density [2]. The third aspect
of the program will focus on device
construction, integration and
proto-typing. The significance of
the program is that while the
microelectronic industry has made
rapid progress in following the
Moore’s law, is it possible that the
energy storage sector can follow
suit if we adapt micro-fabrication
strategies in energy storage
technologies?
Skills to be acquired in this
project: micro-/nano-fabrication,
electrochemistry, system design for
energy storage devices
MOF/Graphene Composites:
Metal Organic Frameworks (MOFs) are crystalline,
open-porous materials consisting of
metal ions or metal-oxo units
coordinated by electron donating
organic ligands and possess very
high surface area (~7000 m2/g)
well defined pore sizes and tailorable
structure. However, their
electrochemical charge storage
properties are poor because of their
poor electron conductivity. The
research theme will explore the
synthesis of different MOFs and
formation of intimately mixed
composites with graphene in bulk
scale quantities. This will be
followed by characterization of the
material and investigation of their
charge transport, mass transport and
electrode kinetics using a variety
of electrochemical techniques such
as cyclic voltammetry, impedance
spectroscopy, galvanostatic
polarization, and
spectro-electrochemistry. Given the
rich family of MOFs known today and
the ability to tailor their
structure during synthesis there is
potential for generation of
extensive fundamental data and
applications to be realized for high
energy and high power density
super-capacitor materials [3].
Graphene-based fluidic systems
program - from compact
micro-/nano-fluidic devices to large
area filtration membranes:
The fluidics program deals with
fundamental aspects of fluid-phase
processing of 2D materials. and
applied aspect of fluid and mass
transport through layered 2D
structures in the form of films,
granules and micro-/nano-fluidic
devices.
Graphene membrane development and
application:
GO has rich colloidal phase
behaviour because of its large
lateral dimension to thickness ratio
and exhibits phase transitions from
isotropic to nematic liquid
crystalline phases [4] depending
upon concentration of GO and pH. GO
is also a very flexible molecule
with a small persistence length and
non-conservatively can be considered
as a polymeric fluid. Using
techniques such as
orientation-mapped polarized light
microscopy and rheology we determine
how these materials can be processed
into macroscopic structures such as
films, droplets, granules or fibers
by industrially-relevant
manufacturing approaches [5]. Based
on fundamental understanding between
processing and property we have
developed scalable roll-to-roll
process for the manufacture of
multi-layer graphene-based membranes
[6]. Graphene based membranes have
unique combinations of chemical
inertness, fouling resistance, fast
water transport in the liquid and
vapour phase, nanoscale capillaries,
tunable molecular weight cut-off
with tremendous potential in
nanofiltration and pervaporation
that could solve separation problems
for e.g. in recovery of precious
metals and expensive chemicals in
challenging environments and
dehydration of organic-water
mixtures. Given our demonstrated
ability to manufacture these
membranes with massive scalability,
we will next focus on realizing
these applications. Additionally
through collaborations with
simulation experts we will unravel
the fundamental aspects of molecular
transport through these membranes
structures which has been the
subject of intense research in the
past few years [7].
Skills to be
acquired in this project: polarized
light microscopic imaging, rheology,
membrane fabrication, membrane
transport
Engineered Adsorbents: Emanating from our ability to process the solution-stabilized
graphene sheets is our ability to
easily form 3D structures such as
granules by coating over an existing
granular structure such as a sand
grains or an adsorbent granule. We
have previously demonstrated the
utility of these granular structures
as filtration materials in
column-based filtration [8]. Given
that the coating chemistry can be
tuned by the functional groups and
mass transport controlled by the
porosity of the assembled
structures, a wide variety of
pollutants could be targeted. Among
them sequestration of trace organics
and mercury from pollution streams
will be of immediate significance.
It is expected that significant
industrial interest can be generated
in this research program.
Skills to be acquired in this
project: Graphene chemistry,
adsorptive separation technologies
Micro-/Nano-Fluidics:
Graphene-based multilayer thin films
are exciting new materials for
fluidic systems because these films
form ensemble nano-capillaries
between each individual graphene
sheet of ~ 1nm regardless of the
size of the graphene microplates and
the size of the continuous films.
These films can be positioned
directly on a substrate at precise
locations with dimensional control
of hundreds of microns by simple
masking processes, but these films
contain assembled nanoscale
capillaries which are permselective
[9]. The abilities to precisely
place these nanocapillaries enables
us to integrate nanofluidics with
microfluidics, thus opening up a
host of possibilities in fundamental
understanding of ion-transport
behaviour such as electrosmosis,
electrophoresis and ion-current
rectification [10],
while empowering us to
effectively use these nanoscale
phenomena in chip-based separations
by interfacing with microfluidics
and surface functionalization
chemistries.
Skills to be acquired in this
project:
Microfluidics, nanofluidic transport
measurement.
References (published by our research
group along with collaborators)
[1]
D. E. Lobo, J.Fu, T.Gengenbach,
M. Majumder, "Localized
Deoxygenation and Direct Patterning
of Graphene Oxide by Focused Ion
Beams”
Langmuir,
2012,
28,
41,14815–14821
[2] D.E.Lobo,
P.Chakraborty-Banerjee, C.Easton,
M.Majumder, “Miniaturized
In-plane Electrode Systems of
Reduced Graphene Oxide with Enhanced
Energy and Ultra-high Power
Densities by Focused Ion-beam
Engineering”
Advanced Energy
Materials, (in
press)
[3] P. Chakraborty-Banerjee,
D.E.Lobo, R.Middag, W.K.Ng,
M.Majumder, “Electrochemical
Capacitance of Ni-doped MOF-5 and
reduced graphene oxide composites:
More than the sum of its parts”,
ACS Applied Materials and Interfaces, 2015,7,6,3655-64
[4] R.Tkacz,
R.Oldenbourg, S.B. Mehta, A. Verma,
M.Miansari, M.Majumder, "pH Dependent Isotropic to Nematic Phase Transitions
in Graphene Oxide Dispersions Reveal
Droplet Liquid Crystalline Phases",
Chem.Commun,
2014,50,
6668-6671
[5]
R.Tkacz, R.Oldenbourg, A.Fulcher,
M.Miansari,
M.Majumder, "Capillary-Force
Assisted Self-Assembly (CAS) of
highly Ordered and Anisotropic
Graphene-Based Thin Films",
J.Phys.Chem.C,
2014,
118 (1), 259–267
[6]
M.Majumder,
A. Akbarivakilbadi, “A method for
producing graphene and graphene
oxide membranes”, Australian
Provisional Patent, 21 Nov, 2014
[7]
M.Majumder
and B.Corry, “Anomalous Decline
of Water Transport in Covalently
Modified Carbon Nanotube Membranes”,
Chem.Commun, 2011, 47,
7683-85
[8] W.Gao,
M. Majumder, L. Alemany, T. Narayanan, M. Ibarra, B.K. Pradhan,
P.M. Ajayan, “Engineered Graphite
Oxide Materials for Application in
Water Purification”
ACS Applied Materials and Interfaces,
2011,3,
6,1821–1826
[9]
M.Miansari, J.R.Friend. P.Chakraborty-Banerjee,
M.Majumder, L.Y.Yeo, "Graphene-based planar
nanofluidic rectifier",
J. Phys. Chem. C,
2014,
118
(38), 21856–21865
[10]
S.Martin,
A.Neild,
M.Majumder,"Graphene-based
ion rectifier using macroscale
geometric asymmetry",
APL Mat. 2,
092803, 2014 - Special Topic in 2D
Materials.
|